The authors agree that this surname has as its base the medieval name Guadagno, of an auspicious and congratulatory character, documented in Tuscany during the 12th and 13th centuries in the Latin form Guadagnus. That name could function as an autonomous personal name or as a hypocoristic of Buonaguadagno, and expressed a wish for prosperity for the child.

A. Bongioanni considers it synonymous with Avanzo and includes it among the medieval "meaningful" names of the same intent. He further notes that in Piedmont the derived surnames Avagnina, Vagnino and Vagnone arose from this name. As for geographical distribution, the surname appears sporadically in central and north-eastern Italy; the variant Guadagnìn is linked to Veneto; the forms Guadagna, Guaragno and Guadagnuolo correspond to southern Italy and in particular to the Naples area.